Analytisches Screening und Bewertung von marktüblichen "postconsumer"-PET-Recyclaten für die erneute Anwendung in Lebensmittelverpackungen

Due to the increasing market share of soft drink bottles made from poly(ethylene terephthalate) (PET), the recycling of PET for new food packaging applications is gaining more and more economic interest. However, in order to meet the challenging food regulatory requirements, a rapid and efficient analytical quality assurance is necessary to recognize any foreign and unwanted compounds in the PET material. Moreover it is required to have knowledge about real life contaminants concentrations in market PET recyclates in order to allow an assessment whether such PET recyclates can be further processed to obtain purified recyclate products of virgin material like quality suitable for direct food contact packaging applications. The aim of this study was to determine the current status quo of market-usual PET flakes with respect to their migration relevant foreign compound potential. The establishment of an analytical method suitable for quality assurance checking was another aim. For this pu rpose approx. 150 PET samples originating from 14 European PET recyclers and recyclate converters have been investigated. From each of the PET samples an analytical GC fingerprint was made which was qualitatively evaluated. In addition, acetaldehyde and limonene were specifically quantified. As a result, it was shown that the investigated "post-consumer" PET samples as obtained from conventional recycling processes are not as such already suitable for direct food contact. The threshold concentration in the PET material as proposed by US-FDA was found to be exceeded in numerous cases for several substances. On the other hand, these substances were identified in the major cases to be aroma constituents of soft drinks of no toxicological concern. Limonene, as an example, was found to occur in a concentration range from 1.5 to 11 ppm in the PET flakes. The investigated PET samples were of good and very homogeneous quality, thus being promising candidate materials for inclusion in a sandwi c k structure behind a functional barrier. In any case, however, the observed material qualities can serve or be used as input material for further purification processes. Given sufficient cleansing efficiency of such a process, in this way "post-consumer" PET recyclate qualities can be obtained which should be suitable for new direct food contact packaging applications. The same holds true and even more clearly for the investigated industrial scrab samples which are almost comparable to virgin PET quality. The acetaldehyde concentrations were, however, found to be significantly higher in scrab samples. In opposite, PET samples obtained from the German DSD recollection system turned out as not suitable for food packaging. The reasons can be seen in the low polymer type purity and the relatively high fractions of foreign compounds resulting from former technical bottle contents. Concerning the analytical methodology the established headspace GC procedure has been proven to be the most s ui table approach to solve the problem. The low limits of detection achieved with this methodology do allow an evaluation and certification of PET recyclates for this highly challenging and sensitive re-application in food packaging